More teens than ever aren't getting enough sleep

A new study finds young people are likely sacrificing sleep to spend more time on their phones and tablets

"Teens' sleep began to shorten just as the majority started using smartphones," said Twenge, author of iGen: Why Today's Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy -- And Completely Unprepared for Adulthood. "It's a very suspicious pattern."

Students might compensate for that lack of sleep by dozing off during daytime hours, adds Krizan.

"Our body is going to try to meet its sleep needs, which means sleep is going to interfere or shove its nose in other spheres of our lives," he said. "Teens may catch up with naps on the weekend or they may start falling asleep at school."